Make sure the user exists

Signed-off-by: snipe <snipe@snipe.net>

app/Models/ConsumableAssignment.php

@@ -3,13 +3,19 @@
 namespace App\Models;
 
 use Illuminate\Database\Eloquent\Model;
+use Watson\Validating\ValidatingTrait;
 
 class ConsumableAssignment extends Model
 {
     use CompanyableTrait;
+    use ValidatingTrait;
 
     protected $table = 'consumables_users';
 
+    public $rules = [
+        'assigned_to'        => 'exists:users,id',
+    ];
+
     public function consumable()
     {
         return $this->belongsTo(\App\Models\Consumable::class);